Apple is looking into reports of sound problems with its popular iPod mini digital music player.

According to online postings, some people have had trouble with the headphone jack, leading to screeching sounds and static.

Apple said it was aware of "a few isolated reports", saying the device was covered by a one-year warranty.

The credit card sized player, launched in the US in February, can store up to 1,000 songs and costs $249.

Jack issues

According to comments on the enthusiast site iPodLounge, the problems with the player relate to the 10 connector pins that link the main electronics board in the device to a smaller one that attaches to the headphones socket.

If a customer has any technical issues, they should contact AppleCare

Apple spokesman

In postings, users said that the player started making a crackling noise after about a month of use.

"My iPod mini after two weeks of gentle use started to make horrible static noises," wrote Princeton biologist Irakli Loladze in a posting on iPodLounge.

"Sometimes sound will disappear completely. Then the sound will return to normal, but any pressure as small as thumb pressure anywhere on iPod mini will make sounds to come back."

Apple has acknowledged that some people have been having problems with the device, which comes with a standard one year warranty and 90 days of free technical phone support.

"If a customer has any technical issues, they should contact AppleCare," said a company spokesman.

High demand

The little sister to the best-selling iPod went on sale in the US in February. The iPod is the most popular digital music player in the world and more than two million have been sold worldwide.

The iPod mini has so far been a big success for Apple, with reports of shops being out of stock and a thriving export trade on auction site eBay.

Last month, the California company said it had delayed the global launch of the player by three months due to high demand in the US.

Apple may release sales figures for the iPod mini when it reports earning on Wednesday. The player had more than 100,000 orders before it even went on sale.